A high pressure,high temperature study of 1,1-diamino-2,2-dinitro ethylene

We report a synchrotron energy-dispersive X-ray diffraction study of the novel high explosive 1,1-diamino-2,2-dinitroethylene at high pressures and high temperatures. Pressure was generated using a Paris–Edinburgh cell to employ larger sample volumes. High temperatures were created using a resistive graphite cylinder surrounding the sample. The PT phase diagram was explored in the 3.3 GPa pressure range and in the ～ 400°C temperature range. We believe that the sample commenced in the α-phase and then ended up in an amorphous phase when the temperature increased beyond 280°C near 2 GPa, which we believe to be the γ-phase. Further pressure and temperature cycling suggests that the sample transformed reversibly into and out of the amorphous phase near the phase line.     

Three zone furnace for crystal growth under high pressure

Abstract

A special furnace with programmable temperature gradient was contructed. It can be arranged inside an internally heated gas pressure chamber. In this work, the application of the furnace to obtain mercury telluride crystals is presented. Experiments were carried out under gas pressure of argon or nitrogen up to 1,5 GPa in a gas chamber of 30 nun internal diameter; the temperature range used was 25°C–800°C. Since graphite heating elements are used, higher working temperatures are possible. Quasi linear temperature gradient determined by three independent thermocouples can be programmed by the power control systems (i.e. Eurotherm units for the three regulation zones).     

Structure and Characteristics of the Fracturing of Layered Ni-Al Composites

Layered composite materials with alternating layers of a solid solution of aluminum in nickel and intermetallic Ni-Al compounds are obtained. The evolution of the composite structures depending on the heat-treatment conditions is discussed. The mechanical tests of materials highlight a fracture toughness of up to 23 MPa m^1/2, a strength of up to 1800 MPa at room temperature and 150–480 MPa in the range 1000–1150°C.     

Interactive effect of pressure and temperature on the preservation of rat primary-cultured astrocytes and human glioblastoma cell line A172

Environmental factors such as temperature and pressure are important determinants of cell survival. Although the effect of temperature on cell preservation has been previously reported, the effects of pressure, an equally important thermodynamic parameter, have not been sufficiently investigated. In this study, we investigated the effect of temperature and pressure on cellular viability, morphology, adhesiveness, cell death, cell cycle and glucose metabolism in rat primary-cultured astrocytes and A172 human glioblastoma cell line subjected to 4-day preservation. It was revealed that under favorable preservation conditions (temperature: 15°C–20°C, pressure: 0.1–30?MPa) (1) cell morphology and adhesiveness of preserved cells were maintained similar to freshly isolated cells; (2) cell cycle was arrested; (3) glucose uptake and intra/extra-cellular pH decrease were suppressed. These results suggest that lowering temperature to 15°C–20°C or increasing pressure up to 30?MPa at temperatures of 20°C–25°C can reduce cellular metabolism and maintain cell-membrane fluidity, thus resulting in higher viability.     

Behavior of thermocouples under high pressure in a multi-anvil apparatus

We have conducted experiments to study the behavior of W5%Re–W26%Re (type C) and Pt10%Rh–Pt (type S) thermocouples under high pressure in a multi-anvil apparatus. The electromotive force (emf) between four different or three identical thermocouple wires was measured up to 15?GPa and 2100?°C. Mechanical and chemical stability of the thermocouples was examined during and after the experiments. Due to the effect of pressure on the emf/temperature relation, the temperature reading of the type C minus that of the type S thermocouple rises to +5?°C then falls to ?15?°C between room temperature and 1500?°C at 5?GPa, and to +25?°C and then ?35?°C between room temperature and 1800?°C at 15?GPa. In addition, we observed variations in the emf/temperature relation caused by uncertainties in the position and geometry of hot junctions in a steep temperature gradient, and by variable distribution of pressure gradient and non-hydrostatic stress on the thermocouple wires. These errors are estimated at 1.6% for the type S thermocouple up to 1700?°C, and 0.8% for the type C thermocouple up to 2100?°C. Self-diffusion and chemical contamination of the thermocouples by high-purity insulating ceramics appear negligible for the type S thermocouple at 1700?°C for one hour, and for the type C thermocouple at 2100?°C for half an hour. In contrast, large-scale displacement of the hot junction due to dislocation of the type C thermocouple wires and plastic deformation of the type S thermocouple wires may lead to large errors in temperature measurement (±200?°C).     

The thermal conductivity of three polyatomic gases and air at 27.5°C and pressures up to 36 MPa

The paper reports accurate measurements of the thermal conductivity of ethane, ethylene, nitrous oxide, air and argon-free air as a function of density at a temperature of 27.5°C. In the case of ethane the experimental data extend over the pressure range 0.6–3.4 MPa, for ethylene over the range 0.6–5 MPa and for nitrous oxide over the range 0.6–4.5 MPa. The measurements on the two samples of air cover the range 0.8–36 MPa. All the measurements have been carried out in a transient hot-wire instrument and have an estimated uncertainty of ±0.2%.For air the few experimental data that exist deviate by up to 5% from the present results which are to be preferred owing to their higher accuracy. In the case of the pure gases the experimental data are combined with accurate viscosities and employed to estimate collision numbers for rotational relaxation in the gases.     

Self-Reinforced High-Density Polyethylene Prepared by Low-Frequency,Vibration-Assisted Injection Molding. 1. Processing Conditions and Physical Properties

Using a low-frequency, vibration-assisted injection molding (VAIM) device, the effects of vibration variables (frequency and amplitude) on mechanical properties and thermal softening temperature of high-density polyethylene (HDPE) injection moldings were investigated. For VAIM-processed samples, the mechanical properties can be improved by changing vibration frequency and vibration pressure amplitude. Injected at a constant vibration pressure amplitude, a low range of frequency (below 0.7 Hz) was favorable for increasing yield strength; in the high range of frequency (0.7 Hz < f < 2.33 Hz) the yield strength remained at a plateau. Injected at a constant frequency (0.7 Hz) the yield strength increased sharply with decreased elongation when applying large vibration pressure amplitude. The maximal yield strength and Young's modulus were 60.6 MPa and 2.1 GPa for a VAIM sample compared with 39.8 MPa and 1.0 GPa for a conventional injection-molded (CIM) sample, respectively; there was also a 10°C increase in Vicat softening point temperature.     

Application of indium tin oxide (ITO) thin film as a low emissivity film on Ni-based alloy at high temperature

Indium tin oxide (ITO) films as the low emissivity coatings of Ni-based alloy at high temperature were studies. ITO films were deposited on the polished surface of alloy K424 by direct current magnetron sputtering. These ITO-coated samples were heat-treated in air at 600–900 °C for 150 h to explore the effect of high temperature environment on the emissivity. The samples were analyzed by X-ray diffraction (XRD), SEM and EDS. The results show that the surface of sample is integrity after heat processing at 700 °C and below it. A small amount of fine crack is observed on the surface of sample heated at 800 °C and Ti oxide appears. There are lots of fine cracks on the sample annealed at 900 °C and a large number of various oxides are detected. The average infrared emissivities at 3–5 μm and 8–14 μm wavebands were tested by an infrared emissivity measurement instrument. The results show the emissivity of the sample after annealed at 600 and 700 °C is still kept at a low value as the sample before annealed. The ITO film can be used as a low emissivity coating of super alloy K424 up to 700 °C.     

Investigation of toluene LIF at high pressure and high temperature in an optical engine

Toluene laser-induced fluorescence (LIF) emission spectra were acquired in an optical engine with excitation at 248 nm. Toluene was homogeneously seeded in pure nitrogen and air which were used as intake gases. Data were acquired during the compression phase without ignition leading to simultaneous increases in temperature and pressure from 20°C and 1 bar to 500°C and 23.6 bar. Compared to LIF emission spectra at high temperature and atmospheric pressure reported in the literature, the toluene-LIF emission signal shifts to longer wavelengths when temperature and pressure increase simultaneously, whereas the spectrally integrated emission intensity is slightly affected by the pressure level.     

Preparation of Mg55Ni35Si10 Amorphous Powders by Mechanical Alloying and Consolidation by Vacuum Hot Pressing

Amorphous Mg55Ni35Si10 powders are fabricated by using a mechanical alloying technique. The amorphous powders are found to exhibit a relatively high crystallization temperature of 380℃. The as-milled amorphous Mg55Ni35Si10 powders are consolidated successfully into bulk body by vacuum hot pressing technique. Limited nanocrystallization is noticed. The Vickers microhardness range of the Mg55Ni35Si10 bulk sample is 7834 to 8048 MPa. Its bending strength and compressive strength are 529 MPa and 1466 MPa, respectively.     

Investigations of texture formation in geomaterials by neutron diffraction with high pressure chambers

Abstract

This paper suggests a classification of texture in quartzitic rocks. Possible mechanisms of texture formation and their relation to tectonic processes are discussed.

A scheme for the experimental varification of some models describing the evolution of deformation structures in geological materials in dependence on various erxternal conditions (high pressures, temperatures, various loadings, etc.) acting on a sample is proposed.

To investigate “in situ” the mechanisms of texture formation in rocks, high pressure devices are under construction. They will be built of a special T_i ? Z_r alloy, which has zero coherent scattering lenght and therefore is well suited for neutron diffraction investigations. Two different devices are proposed. The first one allows neutron diffraction measurements of sample volumes up to 4 cm³, a hydrostatic pressure of 1, 5 GPa, a temperature of 300° C, and uniaxial compression up to 50 kN. Pressure temperature and axial load are measured inside the chamber. Besides during the experiment, diagrams of load, elastic wave velocities and acoustic emission will be recorded. The second chamber is designed to investigate the mechanisms of texture formation in polycrystal samples (rocks or their imitations) at temperatures up to 800° C and axial compression with a force of up to 150 kN.     

Temperature dependent electrophysical characteristics of GaAs-polymer composite varistors

A composition of GaAs-polymer tiny particles was pressed at a temperature of 130 °C and a pressure of 60 MPa and its current–voltage characteristic was studied. The result shows that the prepared disk has varistor behavior and can therefore be used to protect circuits from low overvoltage transients higher than 62 V. Temperature dependence of current-voltage characteristic and the electrical conductivity of the sample were investigated in the temperature range of 25–100 °C. It has been found that increase in temperature results in lower breakdown voltage and nonlinearity coefficient. At high temperatures, nonlinearity in the I–V characteristic of sample disappears and the conductivity becomes Ohmic in nature. The sample has hysteresis which decreases through increase in temperature. Annealing effect on leakage current and breakdown voltage was both investigated and analyzed using SEM micrographs. Finally, the electrical bandgap of the sample was measured.     

Moderate hydrostatic pressure–temperature combinations for inactivation of Bacillus subtilis spores

We report the effect of using moderate hydrostatic pressure, 40–140?MPa, at moderate temperature (38–58°C) to inactivate Bacillus subtilis spores in McIlvaine's citric phosphate buffer at pH 6. We have investigated several parameters: pressure applied, holding time, pressure cycling, and temperature. The kinetics of spore inactivation is reported. The results show that spore inactivation is exponentially proportional to the time the sample is exposed to pressure. Spore germination and inactivation occur at the hydrostatic pressures/temperature combinations we explored. Cycling the pressure while keeping the total time at high pressure constant does not significantly increase spore inactivation. We show that temperature increases spore inactivation at two different rates; a slow rate below 33°C, and at a more rapid rate at higher temperatures. Increasing pressure leads to an increase in spore inactivation below 95?MPa; however, further increases in pressure give a similar rate kill. The time dependence of the effect of pressure is consistent with the first-order model (R²?>?0.9). The thermal resistance values (Z_T) of B. subtilis spores are 30°C, 37°C, and 40°C at 60, 80, 100?MPa. The increase in Z_T value at higher pressures indicates lower temperature sensitivity. The pressure resistance values (Z_P) are 125, 125 and 143?MPa at 38°C, 48°C, and 58°C. These Z_P values are lower than those reported for B. subtilis spores in the literature, which indicates higher sensitivity at pressures less than about 140?MPa. We show that at temperatures <60°C, B. subtilis spores are inactivated at pressures below 100?MPa. This finding could have implications for the design of the sterilization equipment.     

High pressure studies on hesperitin production with hesperidinase free and immobilized in calcium alginate beads

The use of high pressure for the enzymatic synthesis of pharmacologically interesting molecules is a very important tool. Hesperidin and hesperitin exhibit anti-inflammatory, antimicrobial, antioxidant, and anticarcinogenic properties and prevent bone loss. However, hesperidin has a low bioavailability compared with hesperitin, due to the rutinoside moiety attached to the flavonoid. The aim of this work was the enzymatic production of hesperitin from hesperidin (soluble and insoluble) with hesperidinase free and immobilized in Ca-alginate beads, under high pressure conditions. The work was focused on the optimization of enzyme activity, studying the effects: pressure (50–150 MPa), temperature (35–75 °C), concentration of substrate (100–800 mg/L), and immobilization of hesperidinase. An 18-fold increase in hesperidinase residual activity was observed under high pressure conditions of 100 MPa compared to 0.1 MPa. A higher specificity of the hydrolytic reaction under high pressure (100 MPa) with a two-and three-fold increase in the ratio K _cat/K _M (specificity constant) at 55 °C and 75 °C was observed. A two-fold increase in the maximum activity at 100 MPa was observed with immobilized hesperinase compared to 0.1 MPa. In the second reutilization, almost a four-fold increase was obtained under high pressure conditions in comparison to atmospheric pressure.     

Effects of pressure and temperature on the survival rate of adherent A-172 cells

Preservation of cells under high pressure is an important alternative to cryopreservation. We studied the effect of temperature (4, 25, 37°C) and pressure (0.1–350 MPa) on the survival rate of A-172 glioblastoma cells. The survival rate was not changed by brief (10 min) pressurization of up to 150 MPa, but the survival rate began to decrease from 150 MPa, and most of the A-172 cells died when treated with over 200 MPa. Lengthy pressurization (4 days) at lower pressure (upto 20.1 MPa) without medium exchange showed complex results. The survival rate of cells preserved at 25°C showed two maxima at 1.6 and 20.1 MPa. After preservation, cells adhered and proliferated in the same way as normal cells when cultured at 37°C in a CO₂ incubator. The other two temperatures, 4° and 37°C, showed no maximum survival rate. Therefore, a high survival rate can be maintained with high pressure treatment.     

The thermal and electrical conductivities of metals at high temperatures

A method of investigating the electrical and thermal conductivities of metals at high temperatures is described. The theory of the method depends upon the application of ideas which are fundamental in the study of electrical contact phenomena. The ratio of the thermal to the electrical conductivity of platinum has been determined from 1200° C to the melting point (1773° C) and from the melting point to 2300° C by making simultaneous observations of electrical potential and maximum temperature in a short wire through which current is passed. The wire terminates in two blocks of the same metal, and the ends of the wire are not assumed to be plane isothermal (and equipotential) surfaces. The wire remains in place when partly molten so that observations are extended well into the molten range. The method is independent of the exact geometrical configuration of the conducting system. The details of the arrangement of the apparatus and of the method of temperature measurement are given. The results are discussed in relation to the properties of the molten metal bridges formed between the electrodes of electrical contacts and to the value of theLorenz factor in theWiedemann-Franz law.     

Large volume high pressure research using the wiggler port at NSLS

Abstract

A DIA-type cubic-anvil high pressure apparatus (SAM-85) has been interfaced with white x-ray radiation from the superconducting wiggler port of the National Synchrotron Light Source at Brookhaven National Laboratory. Energy-dispersive x-ray diffraction measurements can be obtained for samples with dimensions of the order of 1 mm as a function of pressure and temperature utilizing x-ray energies of up to100 keV.

The sample environment is examined. Pressure is uniform in the sample chamber to within 0.1 GPa, and temperature is constant in the scattering volume to within 5°C.A method is defined for determining deviatoric stress. We find that for a sample containing NaCl and Au, the deviatoric stress increases to about 0.3 GPa as pressure increases to 1.5 GPa and then remains constant, probably reflecting the strength of the sample. Upon heating, the deviatoric stress quickly approaches zero.

Presented at the IUCr Workshop on ‘Synchrotron Radiation Instrumentation for High Pressure Crystallography’, Daresbury Laboratory 20-21 July 1991     

EPR study of table sugar rod and powder as high dose dosimeters

In order to improve the ease of sample handling, the reproducibility of signal detection and quantification, simple methods of incorporating a homogeneous mixture containing sugar powder (30%) with wax (35%) and rubber (35%) into rods has been adopted. The dose response, the time stability of the free radicals produced in table sugar dosimeters (in both rod and powder form) by gamma radiation and the effect of the temperature during irradiation were studied by EPR (Electron Paramagnetic Resonance). The peak-to-peak height (PPH) measurement of the EPR signal is studied as a function of the absorbed gamma dose in the range 0.1–58 kGy. For the two forms, a linear dependency is found between 0.1 and 26 kGy. At higher doses the EPR signal amplitude continues to grow but non-linear up to 58 kGy. The dependence of temperature during irradiation has been investigated in the temperature range 25–40 °C and the calculated correction coefficients were found (2.7 ± 0.2)% °C^?1 and (1.5 ± 0.3)% °C^?1, respectively, for powder and rod forms. The time stability of the stored sugar samples was investigated for 34 days at room temperature, a rapid decrease of EPR signal was showed immediately after irradiation followed by slowly decrease.     

Effect of high hydrostatic pressure processing and squeezing pressure on some quality properties of pomegranate juice against thermal treatment

The aim of this study was to investigate the effect of high hydrostatic pressure (HHP) treatment (200, 300, 400?MPa; 5°C, 15°C and 25°C; 5 and 10 min) on some quality properties of pomegranate juice. Juice samples are obtained under industrial conditions at two different squeezing pressure levels (100 and 150?psi – 0.689 and 1.033?MPa, respectively). Results are compared against conventional thermal treatment (85°C/10 min) and raw sample. For all three processing temperature, HHP combinations at 400?MPa for 10 min were sufficient to decrease the microbial load around 4.0 log cycles for both squeeze levels. All HHP treatments showed no significant decrease at antioxidant activity, total phenolic content and monomeric anthocyanin pigment concentrations, while there was a significant decrease (p?≤?.05) in thermal-treated samples. Being the highest sugar alcohol in pomegranate juice, mannitol content must be considered for determining the authenticity, and mannitol content increased with squeezing pressure and thermal treatment.     

Deformation and annealing behaviour of a low carbon high Mn TWIP steel microalloyed with Ti

ABSTRACT

A low carbon high Mn, Ti microalloyed dual phase TWIP steel has been processed through cold rolling and annealing. X-ray diffraction reveals the maximum austenite (≈92%) in HRACST sample whereas, the 50CD sample shows 29% ferrite. The microstructure of HRAC and HRACST samples reveal austenite grains with annealing twins and deformation induced ferrite (DIF). The higher amount of DIF along with deformation twins form during cold deformation. Annealing at 500°C shows recovery, whereas at 700°C shows partial recrystallisation and at 900°C reveals almost full recrystallisation. TEM microstructures of the 900°C for 30?min samples reveal annealing twins with TiC particle. Strong Brass {110}<112> and Goss{110}<001> texture components are observed in HRAC, HRACST and 50CD samples. Goss Twin (GT) {113}<332> and Copper Twin (Cu-T) {552}<115> components are observed in 50CD sample. Addition of Ti results in an average grain size of 20?μm. Maximum YS (1176?MPa) and UTS (1283?MPa) values with the lowest ductility of 11% have been obtained for the 50CD sample which is related to the formation of extensive deformation twin and a higher fraction of DIF. 700°C-30?min and 700°C-60?min samples show an increase in ductility (23% and 34%, respectively) with a marginal decrease in tensile strength (1054?MPa). Annealing at 900°C shows ductility restoration up to 60% with higher tensile strength compared to HRACST sample. Ductile fracture of HRAC and HRACST samples transform to brittle fracture in the 50CD sample. Annealing at 900°C for 30?min shows ductile fracture with some (Fe, Mn)S and TiC particles.